I always throw it out there because people don't seem to be aware of it.
Dating and de facto are two different things. The latter is required for an 820/801 and easiest way to prove it is to live together and have combined lives such as joint lease/mortgage, bank accounts, etc. Hard to tell if you'd meet the requirements or if it would be considered dating, but a migration agent can certainly look what you have over and tell you if you'd meet the requirements or not.
PMV route is only $1170 more expensive and does not require de facto evidence so is often the only real partner visa route for engaged couples, especially those that live apart. No point in doing it if you definitely qualify as de facto as you can apply for the 820/801 as a couple, as an engaged couple, or as a married couple. The evidence requirement is the same regardless.
If at the time of application the couple can prove to have been de facto for at least three years prior to applying, then yes the CO can choose to grant the 801 along with 820. This doesn't always seem to happen though and is at the discretion of the CO. Also, that is 3 years DE FACTO. Time dating does not count and it's all about whether a CO thinks what evidence you have is dating or de facto. There are couples who have posted on here recently who showed de facto evidence for 3+ years and still were only granted the 820, so i wouldn't bank on jumping straight to PR without solid evidence.